System and method for fabricating composite laminate structures with co-laminated radar absorbing material

ABSTRACT

Various embodiments provide systems and methods for fabricating composite laminate structures with co-laminated radar absorbing material. An example embodiment includes providing a component part fabricated from composite laminate and having an inside surface and an outside surface; providing a portion of radar absorbing material (RAM) having an inside surface and an outside surface; positioning the outside surface of the component part against the inside surface of the portion of RAM to form an assembly; and applying pressure to the assembly thereby causing the portion of RAM to bond to the outside surface of the component part.

TECHNICAL FIELD

The disclosed subject matter relates to the field of composite laminatesand radar absorbing materials, and more particularly to systems andmethods for fabricating composite laminate structures with co-laminatedradar absorbing material.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever. The following notice applies to the software and dataas described below and in the drawings that form a part of thisdocument: Copyright 2007-2008 Composite Engineering, Inc. (CEI), AllRights Reserved.

BACKGROUND

Advanced composites of layers of polymer or resin-impregnated fibers arecommonly used as a primary structural component in the manufacture of avariety of structures, including airframe components for various typesof aircraft. These materials provide greater structural efficiency atlower weights than equivalent metallic structures. Other uses forcomposite laminates include marine craft, submersibles, land vehicles,stationary structures, and many other applications in mobile orstationary structures or components.

One particular application for which composite laminates are used is thefabrication of airframe components for pilotless aircraft, includingpilotless target aircraft or drones, which are often used for thetraining of military pilots. Given that drones are subject to damage ordestruction when used for their intended purpose, it is important todevelop manufacturing techniques that can produce drone aircraft asinexpensively as possible. For this reason, composites have become apopular choice for drone airframe fabrication. In support of low costmanufacture, it is also important to reduce the need for manual steps inthe assembly of the finished airframe. Manual steps are labor-intensive,expensive, and can lead to finished products that are not uniform.

Drones used for military training are often required to model thephysical, visual, thermal, and electromagnetic characteristics of thehostile aircraft against which pilots are being trained. For thisreason, drones must be manufactured to specific specifications asmandated by a government agency or civilian organization. One of thesespecifications defines a particular radar signature that a drone mustpresent in flight. To meet radar signature specifications, dronemanufacturers can design a drone to be of a particular size and shape.Additionally, the drone can be constructed with radar absorbing material(RAM) covering all or a portion of the exterior of the airframe. The useof RAM enables a drone manufacturer to precisely configure a drone witha desired level of radar reflectivity. The purpose of this material isto absorb radio frequency radiation (e.g. microwave or radar) to preventreflection. Some form of RAM is commonly used on military aircraft,ships, land vehicles, and fixed installations.

Many types of radar absorbing materials are known in the art. Forexample, the U.S. Patents referenced below describe a few RAM compoundsthat can be used for configuring an object with a desired radarsignature. In other implementations, RAM is made from a non-electricallyconductive (dielectric) polymer with dispersed particles of conductiveand/or magnetic particles (typically a form of Iron). Traditionally,this material is made from a cured elastomeric (rubber-like) materialwith an adhesive backing to allow installation on the structure thatrequires this treatment.

Unfortunately, these conventional RAM compounds/materials and associatedmanufacturing techniques are problematic for several reasons. Using oneconventional technique, RAM is sprayed or painted on the exterior of anairframe. However, this technique can only produce a thin layer of RAMon the airframe. If applied too thickly, the RAM is subject to crackingor flaking due to vibration and high airflow in flight. Unfortunately, athin layer of RAM often cannot produce a desired level of radarabsorption.

Using another conventional technique, RAM is manually applied to theexterior of an airframe in strips or pieces cut from a sheet of RAM. TheRAM pieces are typically glued, stapled, or riveted to the airframe.Although this technique can achieve a desired thickness and arrangementof RAM on an airframe, the seams or joins between RAM pieces can peelup, form gaps, or perturb the smooth flow of air across the airframe.Further, this technique does not produce a finished product on which theRAM is tightly and uniformly contoured to the mold shape. The finishedstructure with a RAM layer applied using conventional techniques is notsufficiently durable as the glued-on RAM can create a path for water,air, or other matter that may cause separation of the RAM from the outersurface of the structure. In addition, this technique for applying RAMis labor-intensive and time-consuming.

Using still another conventional technique, RAM is integrated into aformulation of composite material from which a composite laminateairframe is fabricated. This technique avoids the problems associatedwith sprayed-on or glued-on RAM. However, it is sometimes difficult toachieve a desired level of radar absorption with composite-integratedRAM. Further, it is not possible to cover only a portion of the airframeusing this technique. Finally, the integrated RAM can interfere with thestructural integrity of the composite airframe.

U.S. Pat. No. 6,486,822 describes coated ferromagnetic particles, whichare useful as radar absorbing material (RAM). In particular,ferromagnetic particles such as iron, carbonyl iron, cobalt, nickel, andalloys thereof are provided that have been coated with a protectivenon-conducting material such as silicon, silicon dioxide, aluminumoxide, and the like. The ferromagnetic particles are coated in arotating retort containing a gaseous composition that deposits onto ordiffuses into the particle. The coated particles are particularlysuitable for incorporation into RAM coating compositions intended foruse in corrosive atmospheres.

U.S. Pat. No. 5,552,455 describes a radar absorbing material and aprocess for making same. In detail, the technique includes a bindermaterial containing a mixture of two groups of spheres made of amagnetic material, The first group of spheres have an average diameterand the second group have an average diameter generally 0.73 times theaverage diameter of the spheres of the first group. The first and secondgroup contains generally equal numbers of spheres. The amount of thebinder material incorporated is sufficient to both bind mixture togetherwhile maintaining the individual spheres separated from each other.

U.S. Pat. No. 6,411,248 describes a glue-gun applied hot-meltradar-absorbing material (RAM) and method. The hot-melt radar-absorbingmaterial composition comprises: (a) 70 to 85 wt % carbonyl iron powder;(b) 2 to 10 wt % of a metal deactivator; and (c) balance a thermoplasticpolyurethane. The method for repair of a body with a radar-absorbingmaterial, comprises: (a) formulating the hot-melt radar-absorbingmaterial of the present invention; (b) forming the hot-meltradar-absorbing material into a shape; (c) applying the hot-meltradar-absorbing material in a molten state onto the body; and (d)allowing the hot-melt radar-absorbing material to cool to roomtemperature. The shape of the hot-melt RAM is advantageously a “gluestick”, which is configured to go into a glue gun. The repair operatorloads the glue stick into the glue gun and pulls the trigger. The gluegun heats the glue stick, and the molten material is applied to the areato be repaired.

U.S. Pat. No. 6,111,534 describes a structural composite material ableto absorb radar waves at frequencies of 18 GHz, 35 GHz and 94 GHz. Thismaterial comprises at least three layers of non-magnetic, dielectricmaterial obtained by stacks of impregnated plies, including an outerlayer with a low reflection index and losses having an effectivedielectric permittivity of around 3, to promote the penetration of theincident radar waves, an intermediate layer having an effectivedielectric permittivity of around 5, and an inner layer loaded withelectrically conductive particles and having a substantial effectivedielectric permittivity of around 15 to 20. The material may haveapplications in the manufacture of chests for military vehicles, forexample.

U.S. Pat. No. 7,112,299 describes a method of fabricating laminatearticles. A plurality of support templates are arranged to define a partoutline corresponding to the laminate article. An outer surface of aprimary panel to is secured to the plurality of templates. A secondarypanel is arranged in a desired relationship with the primary panel. Avacuum bag is secured to the primary panel to define a vacuum chamber. Avacuum is applied to the vacuum chamber to remove air from between theat least one primary panel and the at least one secondary panel.Optionally, at least one locater peg may be secured to the primary paneland at least one locater hole may be formed in the secondary panel. Inthis case, the secondary panel is displaced relative to the primarypanel such that the at least one locater peg enters the at least onelocater hole.

Thus, systems and methods for fabricating composite laminate structureswith co-laminated radar absorbing material are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments illustrated by way of example and not limitation in thefigures of the accompanying drawings, in which:

FIG. 1 illustrates an example of a tooling frame for supporting atemplate arranged to define a part outline corresponding to a laminatearticle.

FIG. 2 illustrates an example of an uncured laminate article beingplaced upon the upper surface of the template.

FIG. 3 illustrates an example of a vacuum bag being secured to thetooling frame.

FIG. 4 illustrates an example of a cured laminate article that hasconformed to the shape of the template.

FIG. 5 illustrates an example embodiment in which an uncured laminatearticle and a layer of radar absorbing material (RAM) is positioned on atemplate on a tooling frame.

FIG. 6 illustrates an example embodiment in which a vacuum bag can besecured to the tooling frame to enclose the uncured laminate article,the RAM layer, and template in a vacuum chamber.

FIGS. 7-8 illustrate an example embodiment in which the resultingexample composite laminate structure with co-laminated radar absorbingmaterial is shown.

FIGS. 9-14 illustrate other example embodiments of a system and methodfor fabricating composite laminate structures with co-laminated radarabsorbing material in which the uncured laminate article can be set ontop of the RAM layer and an edge of the RAM layer can be tapered.

FIGS. 15-19 illustrate other example embodiments of a system and methodfor fabricating composite laminate structures with co-laminated radarabsorbing material in which a first uncured laminate article can be setadjacent to the RAM layer and a second uncured laminate article can beset on top of the first uncured laminate article and the RAM layer andan edge of the RAM layer can be straight or tapered.

FIGS. 20-21 illustrate other example embodiments of a system and methodfor fabricating composite laminate structures with co-laminated radarabsorbing material in which a plurality of uncured laminate articles canbe set adjacent to a plurality of RAM layers and a second uncuredlaminate article can be set on top of the plurality of uncured laminatearticles and the plurality of RAM layers.

FIG. 22 is a flow diagram illustrating the processing flow for aparticular example embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown,by way of illustration, specific embodiments in which the disclosedsubject matter can be practiced. It is understood that other embodimentsmay be utilized and structural changes may be made without departingfrom the scope of the disclosed subject matter.

According to various example embodiments of the disclosed subject matteras described herein, there are systems and methods described forfabricating composite laminate structures with co-laminated radarabsorbing material (RAM). A particular embodiment relates to a systemand process for fabricating airframe components with co-laminated RAM.Various particular example embodiments are described in more detailbelow.

FIG. 1 illustrates an example of a tooling frame 100 for supporting atemplate 101 arranged to define a part outline corresponding to alaminate article. An outer surface of an uncured laminate article 110,as shown in FIG. 2 can be secured to or placed upon the upper surface ofthe template 101. The uncured laminate article 110 can be conformed tothe shape of the template 101 to ultimately produce a cured laminatearticle in a desired shape. It will be apparent to those of ordinaryskill in the art that template 101 can be cut in any desired shape. Theshape of template 101 shown in FIGS. 1-7 is merely an example shown forillustrative purposes. Once the uncured laminate article 110, as shownin FIG. 3, is installed upon, secured to, or placed upon the uppersurface of the template 101, a vacuum bag 115 can be secured to thetooling frame 100 to enclose the uncured laminate article 110 andtemplate 101 in a vacuum chamber. A vacuum can be applied to the vacuumchamber to remove air from between the vacuum bag 115 and the uncuredlaminate article 110 and from between the uncured laminate article 110and the template 101. The removal of air from the vacuum bag 115 causesthe vacuum bag 115 to apply a uniform pressure to the inner/uppersurface of the uncured laminate article 110 and forcing the uncuredlaminate article 110 to conform to the shape of the template 101. Theuncured laminate article 110 can be allowed to cure and the vacuum bag115 can thereafter be removed. The resulting assembly is shown in FIG.4. As illustrated in FIG. 4, the cured laminate article 111 hasconformed to the shape of the template 101. The completed laminatearticle 111 can be removed from the template 101.

Referring now to FIG. 5, an example illustrates an embodiment of thepresent invention. In the example shown, an uncured laminate article 110and a tooling frame 100 with a template 101 is provided. Additionally, alayer of radar absorbing material (RAM) 120 is also provided. Asdescribed above, the RAM layer 120 can be one of the many types of radarabsorbing materials known in the art. For example, several types of RAMcompounds can be used for configuring an object with a desired radarsignature. In some implementations, RAM layer 120 is made from anon-electrically conductive (dielectric) polymer with dispersedparticles of conductive and/or magnetic particles (typically a form ofIron). RAM layer 120 can also be made from a cured elastomeric(rubber-like) material with an adhesive backing to allow installation ofRAM layer 120 on a surface of the structure that requires thistreatment. In this case as shown in FIG. 5, RAM layer 120 is interposedbetween the outer/lower surface 112 of uncured laminate article 110 andthe upper surface of template 101. In one embodiment, the naturalstickiness of the uncured laminate article 110 can be used as anadhesive to bind the RAM layer 120 to the outer/lower surface 112 ofuncured laminate article 110. In a second embodiment, a separateadhesive material (e.g. epoxy, acrylic adhesive, or the like) can beapplied between the inner/upper surface 121 of RAM layer 120 and theouter/lower surface 112 of uncured laminate article 110 to bind the RAMlayer 120 to the uncured laminate article 110 prior to positioning theRAM layer 120 and the uncured laminate article 110 on template 101. In athird embodiment, a layer or film of pressure-sensitive adhesivematerial (e.g. rubber adhesive or acrylic) can be applied to theinner/upper surface 121 of RAM layer 120 when the RAM layer 120 ismanufactured. Then, when the composite laminate structure withco-laminated radar absorbing material is fabricated, the film ofpressure-sensitive adhesive material on the inner/upper surface 121 ofRAM layer 120 can bind the RAM layer 120 to the outer/lower surface 112of the uncured laminate article 110 prior to positioning the RAM layer120 and the uncured laminate article 110 on template 101. FIG. 5illustrates positioning the RAM layer 120 and the uncured laminatearticle 110 on template 101. FIG. 6 illustrates the application of avacuum bag 115 that can be secured to the tooling frame 100 to enclosethe uncured laminate article 110, the RAM layer 120, and template 101 ina vacuum chamber. A vacuum can be applied to the vacuum chamber toremove air from between the vacuum bag 115 and the uncured laminatearticle 110, from between the uncured laminate article 110 and the RAMlayer 120, and from between the RAM layer 120 and the template 101. Theremoval of air from the vacuum bag 115 causes the vacuum bag 115 toapply a uniform pressure to the inner/upper surface 113 of the uncuredlaminate article 110 and the to the inner/upper surface 121 of RAM layer120 thereby forcing the uncured laminate article 110 and the RAM layer120 to conform to the shape of the template 101. The pressure applied bythe vacuum bag 115 also serves to force the uncured laminate article 110against the RAM layer 120 thereby enabling any of the adhesive methodsdescribed above to permanently bond the uncured laminate article 110 tothe RAM layer 120. The uncured laminate article 110 and separateadhesive, if any, can be allowed to cure and the vacuum bag 115 canthereafter be removed. The resulting example composite laminatestructure with co-laminated radar absorbing material 130 is shown inFIG. 7. As illustrated in FIG. 7, the cured laminate article 111 bondedwith the RAM layer 120 has conformed to the shape of the template 101.As shown in FIG. 8, the completed composite laminate structure withco-laminated radar absorbing material 130 can be removed from thetemplate 101.

FIG. 9 illustrates another example embodiment of a system and method forfabricating composite laminate structures with co-laminated radarabsorbing material. FIG. 9 shows a tooling frame 900 for supporting alaminate article with a RAM layer. An outer/lower surface of the RAMlayer 920 can be placed upon the upper surface of the tooling frame 900.An edge 921 of RAM layer 920 can be tapered to create a better seam withthe uncured laminate article 910 positioned above the RAM layer 920. Theouter/lower surface of the uncured laminate article 910 can be set ontop of the inner/upper surface of RAM layer 920. The pliable uncuredlaminate article 910 will naturally conform to the shape of the RAMlayer 920, including the tapered edge 921, as shown in the example ofFIG. 9. It will be apparent to those of ordinary skill in the art thatRAM layer 920 can be cut in any desired shape.

As shown in FIG. 9, RAM layer 920 is interposed between the outer/lowersurface 912 of uncured laminate article 910 and the upper surface oftooling frame 900. In one embodiment, as described above, the naturalstickiness of the uncured laminate article 910 can be used as anadhesive to bind the RAM layer 920 to the outer/lower surface 912 ofuncured laminate article 910. In a second embodiment, as describedabove, a separate adhesive material (e.g. epoxy, acrylic adhesive, orthe like) can be applied between the inner/upper surface 921 of RAMlayer 920 and the outer/lower surface 912 of uncured laminate article910 to bind the RAM layer 920 to the uncured laminate article 910 priorto positioning the RAM layer 920 and the uncured laminate article 910 ontooling frame 900. In a third embodiment, as described above, a layer orfilm of pressure-sensitive adhesive material (e.g. rubber adhesive oracrylic) can be applied to the inner/upper surface 921 of RAM layer 920when the RAM layer 920 is manufactured. Then, when the compositelaminate structure with co-laminated radar absorbing material isfabricated, the film of pressure-sensitive adhesive material on theinner/upper surface 921 of RAM layer 920 can bind the RAM layer 920 tothe outer/lower surface 912 of the uncured laminate article 910 prior topositioning the RAM layer 920 and the uncured laminate article 910 ontooling frame 900.

Once the uncured laminate article 910 and RAM layer 920 are positionedon the tooling frame 900 as desired, a vacuum bag 915 can be secured tothe tooling frame 900 to enclose the uncured laminate article 910 andthe RAM layer 920 in a vacuum chamber. A vacuum can be applied to thevacuum chamber to remove air from between the vacuum bag 915 and theuncured laminate article 910, from between the uncured laminate article910 and the RAM layer 920, and from between the RAM layer 920 and thetooling frame 900. The removal of air from the vacuum bag 915 causes thevacuum bag 915 to apply a uniform pressure to the inner/upper surface ofthe uncured laminate article 910 thereby forcing the uncured laminatearticle 910 to conform to the shape of the RAM layer 920. The pressureapplied by the vacuum bag 915 also serves to force the uncured laminatearticle 910 against the RAM layer 920 thereby enabling any of theadhesive methods described above to permanently bond the uncuredlaminate article 910 to the RAM layer 920. The uncured laminate article910 and separate adhesive, if any, can be allowed to cure and the vacuumbag 915 can thereafter be removed. The resulting example compositelaminate structure with co-laminated radar absorbing material 930 isshown in FIG. 10. As illustrated in FIG. 10, the cured laminate article911 bonded with the RAM layer 920 has conformed to the shape of the RAMlayer 920 and created a straight and smooth outside surface 931 of thecomposite laminate structure with co-laminated radar absorbing material930. As shown in FIG. 11, the completed composite laminate structurewith co-laminated radar absorbing material 930 can be removed from thetooling frame 900.

FIG. 12 illustrates a particular embodiment of the completed compositelaminate structure with co-laminated radar absorbing material 930wherein a screw or rivet 1201 has been inserted into the exteriorsurface of the structure 930 at or adjacent to the seam or joint 1225between the RAM layer 920 and the composite laminate layer 911 toreinforce the joint and prevent the RAM layer 920 from separating fromthe composite laminate layer 911.

FIG. 13 illustrates a particular embodiment of a system and method forfabricating composite laminate structures with co-laminated radarabsorbing material. FIG. 13 shows a tooling frame 900 for supporting alaminate article with a RAM layer. An outer/lower surface of the RAMlayer 920 can be placed upon the upper surface of the tooling frame 900.As shown in FIG. 13, RAM layer 920 is interposed between the outer/lowersurface 912 of uncured laminate article 910 and the upper surface oftooling frame 900. In the particular embodiment illustrated in FIG. 13,a separate adhesive material (e.g. epoxy, acrylic adhesive, or the like)1325 can be applied between the inner/upper surface 921 of RAM layer 920and the outer/lower surface 912 of uncured laminate article 910 to bindthe RAM layer 920 to the uncured laminate article 910 prior to orconcurrently with positioning the RAM layer 920 and the uncured laminatearticle 910 on tooling frame 900.

Once the uncured laminate article 910 and RAM layer 920 are bonded withadhesive 1325 and positioned on the tooling frame 900 as desired, avacuum bag 915 can be secured to the tooling frame 900 to enclose theuncured laminate article 910 and the RAM layer 920 in a vacuum chamber.As described above, a vacuum can be applied to the vacuum chamber toforce the uncured laminate article 910 to conform to the shape of theRAM layer 920 and to force the uncured laminate article 910 against theRAM layer 920 thereby enabling adhesive 1325 to permanently bond theuncured laminate article 910 to the RAM layer 920. The uncured laminatearticle 910 and separate adhesive 1325 can be allowed to cure and thevacuum bag 915 can thereafter be removed. The resulting examplecomposite laminate structure with co-laminated radar absorbing material1430 is shown in FIG. 14. As illustrated in FIG. 14, the cured laminatearticle 911 bonded with the RAM layer 920 via adhesive 1325 hasconformed to the shape of the RAM layer 920 and created a straight andsmooth outside surface 1431 of the composite laminate structure withco-laminated radar absorbing material 1430.

FIG. 15 illustrates a particular embodiment of a system and method forfabricating composite laminate structures with co-laminated radarabsorbing material. In this example, a first uncured laminate article1511 is placed on an upper surface of tooling frame 900 adjacent to aRAM layer 1520. The RAM layer 1520 and uncured laminate article 1511make contact at seam or joint 1525 and can be bonded together at joint1525 using any of the various adhesive methods described above. Next, asecond uncured laminate article 1510 can be placed on an upper/innersurface of both the RAM layer 1520 and the first uncured laminatearticle 1511 as shown in FIG. 15. The second uncured laminate article1510 can be placed to cover the joint 1525 and provide sufficientsurface area on each side of the joint 1525 to ensure a solid bond toboth the RAM layer 1520 and the first uncured laminate article 1511. Thelower surface 1512 of the second uncured laminate article 1510 can bebonded to the RAM layer 1520 and the first uncured laminate article 1511using any of the various adhesive methods described above.

Once the first uncured laminate article 1511, the second uncuredlaminate article 1510, and the RAM layer 1520 are bonded with adhesive,if any, and positioned on the tooling frame 900 as desired, a vacuum bag1515 can be secured to the tooling frame 900 to enclose the firstuncured laminate article 1511, the second uncured laminate article 1510,and the RAM layer 1520 in a vacuum chamber. As described above, a vacuumcan be applied to the vacuum chamber to force the second uncuredlaminate article 1510 against the RAM layer 1520 and the first uncuredlaminate article 1511 thereby enabling the second uncured laminatearticle 1510 to permanently bond to the first uncured laminate article1511 and the RAM layer 1520. The uncured laminate articles 1510 and 1511and separate adhesive, if any, can be allowed to cure and the vacuum bag1515 can thereafter be removed. The resulting example composite laminatestructure with co-laminated radar absorbing material 1530 is shown inFIG. 16. As illustrated in FIG. 16, the cured laminate article 1511,bonded with the RAM layer 1520, has conformed to the shape of the RAMlayer 1520 and created a straight and smooth outside surface 1531 of thecomposite laminate structure with co-laminated radar absorbing material1530. Further, the joint 1525 has been reinforced with the applicationof the second uncured laminate article 1510.

FIG. 17 illustrates a particular embodiment of a system and method forfabricating composite laminate structures with co-laminated radarabsorbing material. In this example, a first uncured laminate article1711 is placed on an upper surface of tooling frame 900 adjacent to aRAM layer 1720. The RAM layer 1720 and uncured laminate article 1711make contact at seam or joint 1725. In this embodiment, the joint 1725can be tapered to create a better seam with the first uncured laminatearticle 1711 positioned adjacent to the RAM layer 1720. The firstuncured laminate article 1711 can be bonded to the RAM layer 1720 atjoint 1725 using any of the various adhesive methods described above.Next, a second uncured laminate article 1710 can be placed on anupper/inner surface of both the RAM layer 1720 and the first uncuredlaminate article 1711 as shown in FIG. 17. The second uncured laminatearticle 1710 can be placed to cover the joint 1725 and providesufficient surface area on each side of the joint 1725 to ensure a solidbond to both the RAM layer 1720 and the first uncured laminate article1711. The lower surface 1712 of the second uncured laminate article 1710can be bonded to the RAM layer 1720 and the first uncured laminatearticle 1711 using any of the various adhesive methods described above.

Once the first uncured laminate article 1711, the second uncuredlaminate article 1710, and the RAM layer 1720 are bonded with adhesive,if any, and positioned on the tooling frame 900 as desired, a vacuum canbe applied to force the second uncured laminate article 1710 against theRAM layer 1720 and the first uncured laminate article 1711 therebyenabling the second uncured laminate article 1710 to permanently bond tothe first uncured laminate article 1711 and the RAM layer 1720. Theuncured laminate articles 1710 and 1711 and separate adhesive, if any,can be allowed to cure. The resulting example composite laminatestructure with co-laminated radar absorbing material 1730 is shown inFIG. 18. As illustrated in FIG. 18, the cured laminate article 1711,bonded with the RAM layer 1720, has conformed to the shape of the RAMlayer 1720 and created a straight and smooth outside surface 1731 of thecomposite laminate structure with co-laminated radar absorbing material1730. Further, the tapered joint 1725 has been reinforced with theapplication of the second uncured laminate article 1710.

FIG. 19 illustrates a particular embodiment of the completed compositelaminate structure with co-laminated radar absorbing material 1730wherein a screw or rivet 1731 has been inserted into the exteriorsurface of the structure 1730 at or adjacent to the seam or joint 1725between the RAM layer 1720 and the composite laminate layer 1711 toreinforce the joint and prevent the RAM layer 1720 from separating fromthe composite laminate layer 1711.

FIG. 20 illustrates a particular embodiment of a system and method forfabricating composite laminate structures with co-laminated radarabsorbing material. In this example, a plurality of uncured laminatearticles 2011 are placed on an upper surface of tooling frame 900adjacent to a plurality of RAM layers 2020 as shown in FIG. 20. The RAMlayers 2020 and uncured laminate articles 2011 make contact at seams orjoints 2025. In various embodiments, the joints 2025 can be straight,rounded, or tapered to create better seams between the plurality ofuncured laminate articles 2011 and the RAM layers 2020. The plurality ofuncured laminate articles 2011 can be bonded to the plurality of RAMlayers 2020 at joints 2025 using any of the various adhesive methodsdescribed above. Next, a second uncured laminate article 2010 can beplaced on upper/inner surfaces of both the plurality of RAM layers 2020and the plurality of uncured laminate articles 2011 as shown in FIG. 20.The second uncured laminate article 2010 can be placed to cover thejoints 2025 and provide sufficient surface area on each side of thejoints 2025 to ensure a solid bond to both the plurality of RAM layers2020 and the plurality of uncured laminate articles 2011. The lowersurface 2012 of the second uncured laminate article 2010 can be bondedto the plurality of RAM layers 2020 and the plurality of uncuredlaminate articles 2011 using any of the various adhesive methodsdescribed above.

Once the plurality of uncured laminate articles 2011, the second uncuredlaminate article 2010, and the plurality of RAM layers 2020 are bondedwith adhesive, if any, and positioned on the tooling frame 900 asdesired, a vacuum can be applied to force the second uncured laminatearticle 2010 against the plurality of RAM layers 2020 and the pluralityof uncured laminate articles 2011 thereby enabling the second uncuredlaminate article 2010 to permanently bond to the plurality of uncuredlaminate articles 2011 and the plurality of RAM layers 2020. The uncuredlaminate articles 2010 and 2011 and separate adhesive, if any, can beallowed to cure. The resulting example composite laminate structure withco-laminated radar absorbing material 2030 is shown in FIG. 21. Asillustrated in FIG. 21, the cured laminate article 2011, bonded with theRAM layer 2020, has conformed to the shape of the plurality of RAMlayers 2020 and created a straight and smooth outside surface 2031 ofthe composite laminate structure with co-laminated radar absorbingmaterial 2030. Further, the joints 2025 have been reinforced with theapplication of the second uncured laminate article 2010. It will beapparent to those of ordinary skill in the art that the dimensions ofthe plurality of RAM layers 2020 and the plurality of uncured laminatearticles 2011 can be varied to expose a desired amount of RAM on theexterior of a particular structure.

FIG. 22 is a flow diagram illustrating the processing flow for aparticular example embodiment. In the embodiment shown, a method forfabricating composite laminate structures with co-laminated radarabsorbing material includes providing a component part fabricated fromcomposite laminate and having an inside surface and an outside surface(processing block 2205); providing a portion of radar absorbing material(RAM) having an inside surface and an outside surface (processing block2210); positioning the outside surface of the component part against theinside surface of the portion of RAM to form an assembly (processingblock 2215); and applying pressure to the assembly thereby causing theportion of RAM to bond to the outside surface of the component part(processing block 2220).

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of components and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of ordinary skill in the art upon reviewing the descriptionprovided herein. Other embodiments may be utilized and derived, suchthat structural and logical substitutions and changes may be madewithout departing from the scope of this disclosure. The figures hereinare merely representational and may not be drawn to scale. Certainproportions thereof may be exaggerated, while others may be minimized.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

The description herein may include terms, such as “up”, “down”, “upper”,“lower”, “first”, “second”, etc. that are used for descriptive purposesonly and are not to be construed as limiting. The elements, materials,geometries, dimensions, and sequence of operations may all be varied tosuit particular applications. Parts of some embodiments may be includedin, or substituted for, those of other embodiments. While the foregoingexamples of dimensions and ranges are considered typical, the variousembodiments are not limited to such dimensions or ranges.

The Abstract is provided to comply with 37 C.F.R. §1.74(b) to allow thereader to quickly ascertain the nature and gist of the technicaldisclosure. The Abstract is submitted with the understanding that itwill not be used to interpret or limit the scope or meaning of theclaims.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments have more featuresthan are expressly recited in each claim. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separate embodiment.

Thus, as described above, systems and methods for fabricating compositelaminate structures with co-laminated radar absorbing material aredisclosed. Although the disclosed subject matter has been described withreference to several example embodiments, it may be understood that thewords that have been used are words of description and illustration,rather than words of limitation. Changes may be made within the purviewof the appended claims, as presently stated and as amended, withoutdeparting from the scope and spirit of the disclosed subject matter inall its aspects. Although the disclosed subject matter has beendescribed with reference to particular means, materials, andembodiments, the disclosed subject matter is not intended to be limitedto the particulars disclosed; rather, the subject matter extends to allfunctionally equivalent structures, methods, and uses such as are withinthe scope of the appended claims.

1. A method comprising: providing a component part fabricated fromcomposite laminate and having an inside surface and an outside surface;providing a portion of radar absorbing material (RAM) having an insidesurface and an outside surface; positioning the outside surface of thecomponent part against the inside surface of the portion of RAM to forman assembly; and applying pressure to the assembly thereby causing theportion of RAM to bond to the outside surface of the component part. 2.The method as claimed in claim 1 further including applying an adhesivebetween the portion of RAM and the component part.
 3. The method asclaimed in claim 1 further including applying an adhesive film to theinside surface of the portion of RAM.
 4. The method as claimed in claim1 wherein the portion of RAM overlaps only a portion of the componentpart.
 5. The method as claimed in claim 1 wherein an edge of the portionof RAM is tapered.
 6. The method as claimed in claim 1 wherein theportion of RAM is made from a non-electrically conductive polymer withdispersed particles of conductive particles.
 7. The method as claimed inclaim 1 wherein the component part is made from composite layers ofpolymer or resin-impregnated fibers.
 8. The method as claimed in claim 1including applying pressure to the assembly using a vacuum bag.
 9. Themethod as claimed in claim 1 including reinforcing the assembly with ascrew or rivet.
 10. A method comprising: providing a first componentpart fabricated from composite laminate and having an inside surface andan outside surface; providing a second component part fabricated fromcomposite laminate and having an inside surface and an outside surface,providing a portion of radar absorbing material (RAM) having an insidesurface and an outside surface; positioning the first component partadjacent to the portion of RAM; positioning the outside surface of thesecond component part against the inside surface of the portion of RAMand the inside surface of the first component part to form an assembly;and applying pressure to the assembly thereby causing the portion of RAMto bond to the outside surface of the second component part and an edgeof the first component part.
 11. An apparatus comprising: a portion ofradar absorbing material (RAM) having an inside surface and an outsidesurface; and a component part fabricated from composite laminate andhaving an inside surface and an outside surface, the outside surface ofthe component part being pressure bonded to the inside surface of theportion of RAM to form a composite laminate structure with co-laminatedradar absorbing material.
 12. The apparatus as claimed in claim 11including an adhesive for bonding the outside surface of the componentpart to the inside surface of the portion of RAM.
 13. The apparatus asclaimed in claim 11 wherein the inside surface of the portion of RAMincludes an adhesive film.
 14. The apparatus as claimed in claim 11wherein the portion of RAM overlaps only a portion of the componentpart.
 15. The apparatus as claimed in claim 11 wherein an edge of theportion of RAM is tapered.
 16. The apparatus as claimed in claim 11wherein the portion of RAM is made from a non-electrically conductivepolymer with dispersed particles of conductive particles.
 17. Theapparatus as claimed in claim 11 wherein the component part is made fromcomposite layers of polymer or resin-impregnated fibers.
 18. Theapparatus as claimed in claim 11 including a vacuum bag to pressure bondthe inside surface of the portion of RAM to the outside of the componentpart.
 19. The apparatus as claimed in claim 11 including a screw orrivet to reinforce the composite laminate structure with co-laminatedradar absorbing material.
 20. An apparatus comprising: a portion ofradar absorbing material (RAM) having an inside surface and an outsidesurface; a first component part fabricated from composite laminate andhaving an inside surface and an outside surface, the first componentpart being positioned adjacent to the portion of RAM; and a secondcomponent part fabricated from composite laminate and having an insidesurface and an outside surface, the outside surface of the secondcomponent part being pressure bonded to the inside surface of theportion of RAM and the inside surface of the first component part toform a composite laminate structure with co-laminated radar absorbingmaterial.